The present invention relates to safety switches, and to safety switch assemblies.
A safety switch may be considered as an emergency electrical shut off switch, and either allows or prevents electricity from passing through it (i.e. it provides a closed circuit or an open circuit). If the safety switch is activated, such that it forms an open circuit, electricity will not pass to any device to which the safety switch is connected.
Safety switches are often used in places where access to particular enclosures is to be restricted, such enclosures enclosing electrically operated machinery. For example, safety switches are often found in factories that use kinetic machinery powered by electricity. The safety switch may be used to prevent access to an enclosure containing the machinery when the machinery is in operation. Specifically, power will only be supplied to the machinery when the switch is closed, and this is conveniently achieved by the closure of a gate incorporated in the enclosure. When the gate is opened, the safety switch is activated, the circuit is broken, and the electrical power supply to the machinery is interrupted (i.e. the machinery cannot run when the gate is opened and the safety switch is thereby activated). Safety switches are well known in the art, and come in a variety of different forms.
A safety switch will usually comprise a switch mechanism which is housed in a housing and attached to part of a structure forming the enclosure. A protruding actuator (i.e. a key) may be attached to a gate which is movable relative to the enclosure and the safety switch mechanism. When the gate is closed, the actuator engages with the switch mechanism to allow supply of electrical power to the machinery.
While safety switches are intended to be beneficial to workers using and moving around dangerous machinery within a factory, it is not uncommon for the switches themselves to be tampered with. For example, it may be that workers wish to inspect dangerous machinery while it is in operation. In order to do this, they may take off the cover of the safety switch housing and tamper with its internal mechanisms such that the circuit is closed and electrical power supplied to the machinery even when the gate to the enclosure remains open. Alternatively, a worker may obtain a replacement key, or fabricate a makeshift one for him/herself to engage with the safety switch mechanism such that the machinery may be operable even when the gate remains open. Since the purpose of the safety switch is to prevent such access, and to maintain the safety of the workers, tampering with a safety switch or using a replacement key is not desirable.
As stated above, the switch mechanism is housed in a housing and attached to the structure forming the enclosure. It is not uncommon for the switch mechanism to become damaged by repeated use, and in particular damaged by impact from objects such as equipment being carried into and out of the enclosure, or damaged by the gate itself.
It is therefore desired to provide a safety switch to obviate or mitigate at least one of the above-mentioned disadvantages.